The mysterious occurence of when a fan of a band starts to suddenly hate said band as soon as they become popular, appear on MTV, and are heard on the radio. Often, a fall out fan will insist that the band was ruined by mtv, when, in reality, the band has not changed at all except for their popularity status. Usually is in response to all the new teeny bopper fans. Named so for the band Fall Out Boy, which has many fall out fans.

Teeny Bopper: omg did u see (insert band name here) on mtv last nite??? they were lyk pwning!!111
Fall Out Fan: They were only good before mtv TOTALLY RUINED THEM.